feat(config): add interactive settings center

[wendaining]

Summary

• add a bare recall config settings TUI for search bindings, capture rules, appearance, and shell integration
• save TOML changes losslessly and atomically while preserving comments, permissions, newline style, BOM, and symlink targets
• unify pane-width persistence in TOML and migrate the legacy SQLite setting only after a successful save
• support recorded one- or two-chord Ctrl/Alt shortcuts, including Ctrl+Space and PowerShell chord sequences
• reuse the managed shell setup core for Auto, Hooks, and Remove actions

Validation

• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• cargo test
• ./scripts/dev-install.sh --shell zsh
  • verified production installer UI with a locally built release fixture
  • verified automatic proxy and hooks are active
  • exercised all four configuration categories
  • reopened the TUI and confirmed persisted values
  • confirmed output capture and recall doctor
• ./scripts/dev-install.sh --user
  • completed the interactive upgrade flow without importing history
  • kept the existing config and history database
  • verified the installed binary hash matches target/release/recall
  • opened a new zsh and confirmed proxy, hooks, config TUI, and doctor status

Closes #19